Collar stay



FIG. 1 is a perspective view of a collar stay showing my new design;

FIG. 2 is a bottom view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is an end view thereof;

FIG. 6 is an opposite end of FIG. 5; and,

FIG. 7 is a left view thereof. 

CLAIM The ornamental design for a collar stay, as shown and described. 